1. Technical Field
The present invention relates to a light emitting device which emits light by electroluminescence and an electronic apparatus.
2. Related Art
As a thin lightweight light emitting source, an OLED (Organic Light Emitting Diode), that is, an organic EL (Electro Luminescent) element is popular. Accordingly, an image display device having a plurality of the organic EL elements has been developed. The organic EL element has a structure in which at least one organic thin film layer made of an organic material is interposed between pixel electrodes and counter electrodes.
In a field of the organic EL element, there is a known technique (for example, a PCT pamphlet No. WO01/39554) for intensifying light having a specific wavelength in emitted light, using amplified interference, that is, resonance. This technique is capable of improving color purity of luminescent color or improving efficiency of light radiated in response to light emission.
However, the organic EL element has a problem with deterioration of a display image quality caused due to external light reflecting from a display surface. In order to solve this problem, a method of disposing a circular polarizing plate on a display surface side has been suggested, for example. However, since the circular polarizing plate attenuates light generated in a light emitting layer to a half or less, a problem may also occur in that brightness deteriorates.
There has also been suggested a method of reducing reflection of external light by overlapping a color filter with the organic EL element. In this method, the color filter absorbs light having a wavelength other than a wavelength to be transmitted. However, such a method of just using the color filter can reduce the reflection of light having colors different from colors of light emitted by the organic EL element, but cannot reduce the reflection of light having colors similar to colors of light emitted from the organic EL element that much.
Japanese Patent No. 3944906 discloses a technique for adjusting a phase of reflected light of external light in semi-transmissive reflective electrodes of an organic light emitting element and a phase of the reflected light of the external light in reflective electrodes so as to be reversed from each other.
However, Japanese Patent No. 3944906 has a problem in that the reflected light may be reduced due to attenuated interference when the phase of the reflected light in one layer and the phase of the reflected light in another layer are reversed from each other. Moreover, there is a limit to an increase in efficiency of the light emitted from the organic light emitting element under such a condition. In Japanese Patent No. 3944906, the organic light emitting element includes the semi-transmissive reflective electrodes and the reflective electrodes, and has a resonant structure for resonating light by reciprocating the light between such electrodes. However, even in the structure in which light reciprocates between the electrodes, the light is not resonated, and thus use efficiency of light may not be improved if an optical factor such as an optical distance is not appropriate.